Some wireless communication devices—such as smart phones, tablet computers, and laptop computers—contain more than one Subscriber Identity Module (SIM) that provides users with access to a particular mobile telephony network for each SIM card. Examples of mobile telephony networks include GSM, TDSCDMA, CMA2000, and WCDMA. A Dual SIM wireless device is one which holds two SIM cards, which means the device can handle two different network subscriptions. Each network subscription can be assigned to a different account or telephone number. In wireless devices that include only one transceiver, only one of the two subscriptions may be transmitting or receiving radio frequency (RF) signals at a time. Such devices are referred to as Dual SIM Dual Standby (DSDS) devices, since while one subscription is actively transmitting or receiving the other subscription is put on standby. In contrast, in wireless devices that include two transceivers and two SIM cards, referred to as Dual SIM Dual Active (DSDA) devices, both subscriptions may be actively transmitting or receiving at the same time.
Although DSDS devices may be configured with two different network subscriptions (one for each SIM) only one of those subscriptions needs to support a data connection. Unlike voice services that have a specific phone number associated with each subscription, having data services on one subscription is often sufficient to provide all the data services needed by the user independent of the other subscription. With this configuration, a DSDS device may have one network subscription for both data and voice services and the other subscription intended for only providing voice communications. Data services activated on only one subscription and the corresponding network subscription for such data services are referred to herein as the “dedicated data subscription” (DDS). Services that support voice calls only are often referred to as “voice-only service” or “non-DDS services,” and network subscriptions primarily providing voice communications are referred to herein as a “non-DDS”. Network subscription primarily providing voice communications are generally governed by a talk plan and may not include data services. Alternatively, the network subscription primarily providing voice communications may include data services, but just not the preferred data services. Such subscription schemes are often chosen based on data/voice plan costs and/or reliability.
Using conventional DSDS devices such a configuration of subscriptions cannot maintain a data services session (i.e., downloading or uploading data) initiated using one SIM when a voice call is received through the second SIM. Typically, the active data services session on a first SIM must be put on standby in order to activate the voice communication connection on a second SIM. For example, when a traditional DSDS device is downloading a data file (i.e., a music file) using SIM2 and receives a voice call from the network subscription of SIM1, the data download must be discontinued until the voice call has ended.
While DSDA devices enable simultaneous voice and data communications, such devices are generally far more costly and require more power to operate than DSDS devices.